You should add trace on org.jboss.jms.server.plugin (for the JDBCJMSUserManagerService) and mainly org.jboss.security. I *believe* there is something ignoring possible exceptions on org.jboss.security. Maybe some config is affecting it under load. (what about datasource limits?) I'm hoping the trace on org.jboss.security would reveal any exceptions eaten. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4177160#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...